Counterfeits of articles (for example, goods and garments), which are produced by copying the appearances of authentic articles, are being sold and cause problems. Under these circumstances, in order to ensure performance, reliability and security of articles and to maintain the worth of the brands of articles, techniques for verifying the authenticity of the articles are required.
A method in which printing is performed on an article by using special ink or a method in which a chip having special reflection characteristics is applied onto an article may be used as a technique for verifying the authenticity of articles.
In the above method using the special ink printed on an article, for example, a predetermined character or a figure is printed on an article by using an ink, which is fluorescent under ultraviolet light, as the above ink. When ultraviolet light is irradiated on the article, the character or the figure becomes visible on the article, so that the authenticity of the article can be determined. For example, an ink having particles of a magnetic material or magnetized particles mixed therewith may be applied on an article, and the authenticity of the article can be verified by using magnetic sensors.
In the above method using the chip having special reflection characteristics, a chip using optical characteristics of a cholesteric liquid crystal or a hologram formed thereon is used. For example, this technique is disclosed in Japanese Unexamined Patent Applications Publication Nos. S63-51193 and H4-144796.
However, it is somewhat easy to obtain inks similar to various special inks, and anticounterfeiting effects cannot be effectively obtained. Visual holograms, which are sophisticated counterfeits, for which the authenticity thereof is not easily determined by observation, are on the market. Therefore, determination of the authenticity only by using a hologram is difficult.
In view of the increasing sophistication of counterfeiting techniques, a discrimination medium using cholesteric liquid crystal is required which cannot be easily counterfeited and which will provide a good discriminating ability.